This invention relates to blow molding, and more particularly to an improved blow mold in which two or more article molding cavities are formed in each mold fed respectively by two or more parisons.
As will be appreciated by those skilled in the art, blow molding technology is widely used to manufacture hollow plastic articles, such as containers. A parison is formed by extruding a thermoplastic material and the parison is positioned between the separated halves of a mold. The mold halves are closed around the parison and a separation assembly separates the portion of the parison in the mold from the extruded parison outside the mold. Air is injected into the parison inside the mold to press the outer surface of the parison against the inner surface of the mold. When the object thusly formed cools, the mold is opened and the object is ejected from the mold. FIG. 1 illustrates a blow molding machine of the type used in the art, in which a series of molds are carried on a rotating wheel 6. In this machine, the parison is inserted from below into each mold when the mold reaches the nine o""clock position in the rotating cycle. The blow molded object cools as the wheel rotates in a clockwise direction. The mold opens, and the object is ejected, when it reaches the six o""clock position.
In prior vertical wheel blow molding machines of the type just described, typically there is one article forming cavity per mold on the wheel fed by a single parison. In some prior art vertical wheel blow molding applications, molds 7 are used with two article forming cavities 8, as shown in FIG. 2. In this prior art design, both cavities 8 are in line with a single parison injector and are both fed by a single parison.
An object of this invention is the provision of a novel blow mold that increases the capacity of blow molding machines. Another object of the invention is the provision of a novel blow mold that increases the capacity of existing wheel blow molding machines without increasing the manpower to operate them or requiring a substantial increase in capital costs.
Briefly, this invention contemplates the provision of a blow mold in which each mold has two or more cavities, each respectively fed by two or more parisons. Each cavity fed by a separate parison may itself include two or more article cavities aligned with the parison.